Example: Reducing Jitter in Hierarchical CoS Queues

Step-by-Step Procedure

Configure hierarchical scheduling at xe-5.0.0.

1. To configure the VLAN 1 input and output at xe-2/0/0.0 and xe-5/0/0.0:

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   user@host# set interfaces xe-2/0/0 per-unit-scheduler
   user@host# set interfaces xe-2/0/0 flexible-vlan-tagging
   user@host# set interfaces xe-2/0/0 unit 0 vlan-id 1
   user@host# set interfaces xe-2/0/0 unit 0 family inet address 10.1.1.1/24
    
   user@host# set interfaces xe-5/0/0 per-unit-scheduler
   user@host# set interfaces xe-5/0/0 flexible-vlan-tagging
   user@host# set interfaces xe-5/0/0 unit 0 vlan-id 1
   user@host# set interfaces xe-5/0/0 unit 0 family inet address 10.2.1.1/24
   

2. Map each of four queues to a forwarding class.

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   user@host# set class-of-service forwarding-classes queue 0 be
   user@host# set class-of-service forwarding-classes queue 1 ef
   user@host# set class-of-service forwarding-classes queue 2 af
   user@host# set class-of-service forwarding-classes queue 3 nc
   

3. Assign a packet-scheduling priority value to each forwarding class.

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   user@host# set class-of-service schedulers be_sch priority low
   user@host# set class-of-service schedulers ef_sch priority low
   user@host# set class-of-service schedulers af_sch priority strict-high
   user@host# set class-of-service schedulers ef_sch priority low
   

4. Customize the default IEEE 802.1p classifier (BA classifier based on Layer 2 header) by defining different values for iEEE 802.1p code points.

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   user@host# set class-of-service classifiers ieee_jitter forwarding-class be loss-priority low code-points 000
   user@host# set class-of-service classifiers ieee_jitter forwarding-class ef loss-priority low code-points 001
   user@host# set class-of-service classifiers ieee_jitter forwarding-class af loss-priority low code-points 010
   user@host# set class-of-service classifiers ieee_jitter forwarding-class nc loss-priority low code-points 011
   

5. Apply the BA classifier to the input of the logical units on xe-2/0/0.

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   user@host# set interfaces xe-2/0/0 unit * classifiers ieee-802.1 ieee_jitter
   

6. Configure the scheduler map smap_jitter to map the forwarding classes to the schedulers.

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   user@host# set class-of-service scheduler-maps smap_jitter forwarding-class be scheduler be_sch
   user@host# set class-of-service scheduler-maps smap_jitter forwarding-class ef scheduler ef_sch
   user@host# set class-of-service scheduler-maps smap_jitter forwarding-class af scheduler af_sch
   user@host# set class-of-service scheduler-maps smap_jitter forwarding-class nc scheduler nc_sch
   

7. Configure the traffic control profile tcp to combine the scheduler map smap_jitter (that maps the forwarding classes to the schedulers for port-based scheduling) with a shaping rate (for hierarchical scheduling).

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   user@host# set class-of-service traffic-control-profiles tcp scheduler-map smap_jitter
   user@host# set class-of-service traffic-control-profiles tcp shaping-rate 6g
   

8. Apply the traffic control profile to the router output at xe-5/0/0.

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   user@host# set class-of-service-interfaces xe-5/0/0 unit * output-traffic-control-profile tcp
   

9. If you are done configuring the device, commit the configuration.

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   user@host# commit
   

Results

Confirm your configuration by entering show interfaces and show cloass-of-service commands from configuration mode. If the output does not display the intended configuration, repeat the instructions in this example to correct the configuration.

[edit]
user@host# show interfaces
xe-2/0/0 {
    per-unit-scheduler;
    flexible-vlan-tagging;
    unit 0 {
        vlan-id 1;
        family inet {
            address 10.1.1.1/24;
        }
    }
}
xe-5/0/0 {
    per-unit-scheduler;
    flexible-vlan-tagging;
    unit 0 {
        vlan-id 1;
        family inet {
            address 10.2.1.1/24;
        }
    }
}

[edit]
user@host# show class-of-service
classifiers {
    ieee-802.1 ieee_jitter {
        forwarding-class be {
            loss-priority low code-points 000;
        }
        forwarding-class ef {
            loss-priority low code-points 001;
        }
        forwarding-class af {
            loss-priority low code-points 010;
        }
        forwarding-class nc {
            loss-priority low code-points 011;
        }
    }
}
forwarding-classes {
    queue 0 be;
    queue 1 ef;
    queue 2 af;
    queue 3 nc;
}
traffic-control-profiles {
    tcp {
        scheduler-map smap_jitter;
        shaping-rate 6g;
    }
}
interfaces {
    xe-2/0/0 {
        unit * {
            classifiers {
                ieee-802.1 ieee_jitter;
            }
        }
    }
    xe-5/0/0 {
        unit * {
            output-traffic-control-profile tcp;
        }
    }
}
scheduler-maps {
    smap_jitter {
        forwarding-class be scheduler be_sch;
        forwarding-class ef scheduler ef_sch;
        forwarding-class af scheduler af_sch;
        forwarding-class nc scheduler nc_sch;
    }
}
schedulers {
    be_sch {
        priority low;
    }
    ef_sch {
        priority low;
    }
    af_sch {
        priority strict-high;
    }
    nc_sch {
        priority low;
    }
}